Pincers

ABSTRACT

Pincers have a handle portion formed of plastic and gripping members formed of a different material adhesively united to the plastic of the handle portion. Methods include molding the shanks of the gripping members into the handle portions or adhesively bonding the shanks in sockets in pre-molded handle portions.

United States Patent Keniston 1 July 18, 1972 [541 PINCERS FORElGNPATENTS 0R APPLICATIONS Inventor: J Keniston, 0. BOX 690,823 4 1953Great Britain ..s1 43 Franklin, NH. 03235 [22] Filed: June 8, 1970Primary Examiner-Robert C. Riordon Assistant'Examiner-Roscoe V. Parker,Jr. [21] Appl' 44353 AttorneyEdgar H. Kent [52] 0.8. CI ..8l/43 [57]ABSTRACT [51] Int. Cl ..B25b 9/02 [58] Field of Search ..81/43; 128/354;7/1 P; 294/99 Pincers have a handle portion formed of plastic andgripping members formed of a different material adhesively united toRefel'encfis Cmd the plastic of the handle portion. Methods includemolding the UNITED STATES PATENTS shanks of the gripping members intothe handle portions or adhesive-1y bonding the shanks 1n sockets inpre-molded han- 2,41 1,825 1 1/1946 Ferguson ....l28l354 X dle portions.

8/1946 Neugass.... ....128/354 Smith ..8l/43 4 Clains, 7 Drawing figuresPINCERS This invention relates to pincers such as tweezers and forcepsuseful for manipulating small and delicate objects, and particularly topincers formed in large part at least of plastic.

Pincers made of plastic have been proposed prior to this invention buthave failed to attain widespread use for purposes requiring a durableprecision instrument, such as the manipulating of minute or delicateparts in the manufacture of electronic equipment. The reason for suchfailure is, I believe, that no matter what plastic is selected forfabrication of the pincers, they lack one or more of the essentialqualities of such instruments which are provided by the conventional,relatively expensive, all-metal variety; e.g., proper spring, durabilityunder all conditions including high and low temperature, strength, lackof bulk, particularly in the jaws (points), accuracy and uniformity ofjaw registration.

An object of this invention is to provide pincers at least in large partformed of plastic in which the requisite qualities for the purpose areprovided as well as, or better than, by an allmetal construction, andgenerally at a lesser expense.

In attaining these objects the invention features pincers having themanipulating or handle portion made essentially of a plastic which hasall the requisite qualities for that portion and the jaw or pointportions made of a different material, which may be metal or plastic,which has different characteristics that are superior to those of theplastic of the handle portion for satisfying the requirements of the jawor point portions. In the preferred practice of the method the grippingmembers such as the jaw or point portions are preformed with a shankthat is adhesively united with the plastic of the handle portion, eitherby bonding that plastic itself to the shank during the molding of thehandle or by a subsequent ultrasonic bonding treatment, or by anadhesive applied between the shank and the sides of a socket in theformed handle.

The foregoing and other objects and advantages of the invention will beapparent from the following more particular description of preferredembodiments and practices of the invention, taken in conjunction withthe accompanying drawings wherein:

FIG. 1 is a side elevation view of pincers specifically tweezersaccording to the invention;

FIG. 2 is a plan view of the outer side of one of the handle arms and ofthe point united thereto of the embodiment of FIG. 1;

FIG. 3 is a longitudinal section view on line 33 of FIG. 2, looking inthe direction of the arrows;

FIG. 4 is an enlarged transverse section view on line 4-4 of FIG. 2,looking in the direction of the arrows;

FIG. 5 is a view similar to FIG. 4 showing a modification;

FIG. 6 is a plan view of an injection mold cavity for forming an arm andunited point of the embodiment of FIG. 1 according to one method of theinvention;

FIG. 7 is a plan view of a pre-molded arm of the embodiment of FIG. 5before assembling and uniting the point thereto according to othermethods of the invention.

Referring to FIGS. l-4 the pincers there shown has a handle portiondesignated generally 10 which is of plastic composition and ispreferably, for simplicity of manufacture, formed by separately moldingthe two arms designated generally 12 thereof and bonding them togetheradjacent one end thereof. It should be understood however that the twoarms may be molded integral at one of their ends in a more complexmolding operation.

Each of the arms 12 is formed with a flat end portion 14, portions 14being bonded together at their opposed faces as indicated at 16preferably by ultrasonic bonding treatment which causes the plastic onthe two faces to unite, although a separately applied adhesive may beused if desired. Apertures 18 formed in portions 16 are in registry whenarms 12 are in proper alignment, these apertures being used to receivealigning pins of an assembly tool for obtaining and maintaining properalignment of the arms during the bonding of the meeting faces ofportions 14 thereof. Arms 12 are appropriately bowed toward theiropposite ends in portions 20, these ends having adhesively unitedthereto preformed gripping members designated generally 22 by bonding ofthe plastic of the arms with the shank portions 24 of the members. Asshown members 22 have the conventional shape of the points of tweezers.Preferably, as shown, shank portions 24 enlarge laterally toward theirinner ends to provide a positive lock against longitudinal pull-out ofthe points from the handle in addition to the resistance offered by thebonding of the plastic thereto. Preferably also, as shown in FIG. 4,these portions are formed with a bulge or rib 26 at each side to form adovetail joint with the plastic at the sides thereof and are completelyembedded in the plastic between side portions 28 and thinner outer layer30 and inner layer 32 thereof, thus providing a structure highlyresistant to separation of the points from the arms by force applied inany direction. Also, layer 30 may extend beyond side portions 28 andlayer 32 toward the outer ends of the points as shown at 34 to increasethe bond area and structural strength of the joint.

The modification of FIG. 5 differs from that of FIG. 4 in that the shank24 of the point is seated in a closely fitting socket 40 formed in apre-molded arm 12 between side portions 28' and under layer 30' and isunited to the plastic of the walls of the socket and to an extension oflayer 30' corresponding to extension 34in the previous figures by a thinlayer 42 which may be plastic of the handle or a different adhesivebonded to the plastic and to shank 24'. In this embodiment, for ease inmolding and assembly, plastic over one surface of shank 24' as layer 32of the other embodiment, may be omitted.

In a method of forming the embodiment of FIGS. 1-4, an injection moldmember 50 (FIG. 6) may be provided having a main cavity 52 therein whichconforms to the outside surface shape and the thickness of portions 14and 20 of an arm 12, being slightly large, with projecting pins 54 forforming apertures 18. An extension 56 of cavity 52 conforms in size,shape and depth to the extension of a point 22 beyond the end of an arm12, being slightly larger. An indentation 58in the base of extension 56corresponds to extension 34 of plastic layer 30. A top mold member (notshown) may have a complementary inner surface, mating mold cavities 52and 56, which is flat except beyond layer 32 where it steps down to thetop level of the remainder of point 22. In this method the preformedpoint 22 is placed in cavity extension 56 with its shank projecting intocavity 52 as indicated by dotted line 24 so that it is molded into thecorresponding handle portion 12 previously described. It is emphasizedthat the mold cavities, which are normally provided in multiple, shouldbe precision formed particularly at the extension 56 so that the point22 of each arm will be exactly in the same location for accurateregistry of two points when the two arms of a handle are securedtogether.

In a method of forming the embodiment of FIG. 5 a mold member isprovided having a cavity identical with cavity 52 of FIG. 6 but withextension thereof 58 only, extension 56 being omitted. The mating moldmember then differs from that utilized in the method illustrated by FIG.6 in that it has a projection in its under surface corresponding inlocation and complementary in shape to socket 40 of FIG. 5, except that,for convenience of molding and assembly, socket 40 may be formed withoutindentations in its sides and without layer 32. The molded handle arm 12therefore comprises portions 14, 20 and 34 of the embodiment of FIG. 1and socket 40. In assembling a pre-formed point or jaw to a handle armaccording to this method, the shank of the point or jaw is positioned inclosely fitting cavity 40 and there held until the bonding layer 42 hasbeen formed either by ultrasonic treatment causing plastic flow to formlayer 42 or by the setting of a coating of adhesive pre-applied to theshank.

Various plastics have the requisite properties for use as the moldingplastic for fonning the handle portion of the pincers according to theinvention. Phenolics, nylons, and acetal resins may be regarded aspreferred choices, with Delrin, a

trademarked acetal resin of the DuPont Company, being a particularlypreferred choice. The points may be made of metal such as theconventional stainless steel or may be molded of plastic such as certainpolyimide resins that are hard, tough, durable at high and lowtemperatures and acid resistant, a preferred choice being Vespel, atrademarked resin of the DuPont Company, which will withstandtemperatures up to 700 F, has a Rockwell hardness of 79 and a lowcoefficient of friction and is acid resistant. Various adhesives may beemployed for uniting the point or jaw with the plastic of the arm in theFIG. 5 embodiment when a separate adhesive is used, such as some of theepoxy or acrylic cements which are tough and in general form firm bondswith both metal and plastic. A preferred adhesive having the requisitecharacteristics is a methyl-2-cyanoacrylate available from the TennesseeEastman Company under the designation EK-9l0. Like adhesives may be usedfor joining the flat portion 14 of arms 12 if these are notultrasonically bonded.

If desired, metal reinforcing can be included in the plastic handleportion, although with the proper choice of plastic this is really notnecessary and simply adds to the expense, which in most cases issubstantially less than that of all-metal pincers of comparable quality.Also, the gripping members may take any desired or required shape otherthan the flat tweezer points shown in the illustrated embodiment. Othermodifications within the scope of the invention will occur to thoseskilled in the art.

I claim:

l Pincers having the manipulating handle portion formed essentially ofmolded plastic and comprising a pair of joined arms movable toward andaway from one another at their outer ends and a pair of opposed grippingmembers projecting from the outer ends of said arms and being formed ofa different material than the plastic forming said arms, said memberseach having a shank, said arms each having a recess in an outer endportion thereof containing said respective shanks, said outer endportions of said arms having at least substantially the same width asthe remainder of the respective arm, said recesses and shanks beingcorrespondingly enlarged toward their inner ends to prevent longitudinalwithdrawal of said shanks from said recesses, said shanks beingadhesively united with the surrounding plastic of said respective endportions.

2. Pincers according to claim 1 wherein said gripping member shanks areadhesively united with the surrounding plastic by that plastic.

3. Pincers according to claim 1 in which said gripping member shanks andsaid recesses have sidewalls correspondingly bulged and indented to formdovetail joints.

4. Pincers according to claim 1 wherein each arm end portion has alaterally reduced extension overlying and adhesively united to the outersurface of the corresponding gripping member.

* *k l i

1. Pincers having the manipulating handle portion formed essentially ofmolded plastic and comprising a pair of joined arms movable toward andaway from one another at their outer ends and a pair of opposed grippingmembers projecting from the outer ends of said arms and being formed ofa different material than the plastic forming said arms, said memberseach having a shank, said arms each having a recess in an outer endportion thereof containing said respective shanks, said outer endportions of said arms having at least substantially the same width asthe remainder of the respective arm, said recesses and shanks beingcorrespondingly enlarged toward their inner ends to prevent longitudinalwithdrawal of said shanks from said recesses, said shanks beingadhesively united with the surrounding plastic of said respective endportions.
 2. Pincers according to claim 1 wherein said gripping membershanks are adhesively united with the surrounding plastic by thatplastic.
 3. Pincers according to claim 1 in which said gripping membershanks and said recesses have sidewalls correspondingly bulged andindented to form dovetail joints.
 4. Pincers according to claim 1wherein each arm end portion has a laterally reduced extension overlyingand adhesively united to the outer surface of the corresponding grippingmember.